When starting an internal combustion engine in cold ambient temperatures, it is often necessary to regulate the amount of air entering the carburetor. In general, the engine requires a richer fuel to air mixture to start the engine when the engine is cold. Once the engine heats up, a leaner mixture is required. One method of regulating the amount of air entering the carburetor is to control movement of a choke plate rotatably mounted in an interior of the carburetor. The choke plate is typically movable between a closed position wherein the choke plate sbstantially obstructs a flow of air entering the carburetor, and an open position wherein the airflow is substantially unobstructed. When the choke plate is in the closed position, more fuel is drawn into the engine during starting to provide the engine with a richer fuel to air mixture. To start the engine in cold ambient temperatures in a system having a rotatable choke plate, the choke plate is initially placed in a closed position to increase the amount of fuel entering the engine. After the engine is started, the engine requires an increased amount of air and a decreased amount of fuel to avoid stalling, so the choke plate is moved toward a more open position.
In the past, various apparatus have been employed for starts in cold ambient temperatures to automatically move the choke plate to a more closed position during the initial starting and then to a more open position after the engine is started. Conventional automatic choke apparatus and choke pull off devices include apparatus having structure which is electrically operated and apparatus having structure which is vacuum operated. These apparatus also typically include a temperature sensing device which responds to engine temperature sensed and positions the choke plate in a closed position for starting when the engine is cold and then positions the choke plate in an open position once the engine is started and has heated up. However, in those apparatus, the temperature sensing devices are slow to react, requiring some additional structure to move the choke plate to the partially open position immediately after start up before the temperature sensing device has reacted to prevent the engine from stalling. In those conventional apparatus, it is the electrically or vacuum operated structures that move the choke plate to the partially open position immediately after the engine is started to prevent stalling.
As the name suggests, the conventional electrically operated apparatus require the presence of an electrical connection to a source of electrical power to move the choke plate. Similarly, the conventional vacuum operated apparatus require the presence of air pressure differentials to move the choke plate. Oftentimes both the electrically operated apparatus and the vacuum operated apparatus employ intricate and fragile structure requiring a great number of parts to move the choke plate. As a result, both types of apparatus are often costly to manufacture and are prone to failure especially in the harsh environments surrounding most internal combustion engine applications.
It is clear that there has existed a long and unfilled need in the prior art for an automatic choke apparatus and method for automatically controlling movement of the choke plate during cold ambient starts while addressing the above recited problems, or similar problems.